Vipera walser GHIELMI, MENEGON, MARSDEN, LADDAGA & URSENBACHER, 2016
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Vipera walser
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| Higher Taxa | Viperidae, Viperinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes) |
| Subspecies | |
| Common Names | G: Piemont-Viper Italian: vipera dei Walser |
| Synonym | Vipera walser GHIELMI, MENEGON, MARSDEN, LADDAGA & URSENBACHER 2016 Vipera berus walser — SPEYBROECK et al. 2020 Vipera berus walser — SINDACO & RAZZETTI 2021 |
| Distribution | NW Italy (Pennine Alps) Type locality: San Giovanni d’Andorno, strada per Oropa at 1300 m elevation in the Alps north of town of Biella, a subrange of the Pennine Alps, north-western Italy. |
| Reproduction | ovovivparous |
| Types | Holotype: MSNG 34485, Adult female, collected in S. Giovanni d’Andorno, on the road to Oropa in the Biella prealps, at about 1300 m a.s.l. by A. Rosazza in the summer of 1930 (Fig. 5). Paratypes: One adult male: MSNG33638M collected at Monte Rosso del Croso, on 30 August 1933. One juvenile male: MSNG33637B and one subadult male: MSNG30818C collected at Alpe Finestre by Felice Capra, respectively, on 28 July 1930 and 15 August 1928. One adult female: MSNG30818A, one subadult female: MSNG30818B, and two juvenile females: MSNG33637C and MSNG33637D collected by Felice Capra at Alpe Finestre between August 1928 and August 1939. One juvenile female: MSNG30286 collected by F. Capra at Monte Rosso del Croso on 12 September 1934; one adult female MSNG33637A col- lected by F. Capra at Alpe le Piane on 5 August 1937; one adult female MSNG41663 collected by A. Margiocco at Piedicavallo in September 1967. |
| Diagnosis | Diagnosis: Vipera walser sp. nov. is generally similar to the species of the subgenus Pelias and can be confused with V. berus, which co-occurs on the Alps in allopatry (Fig. 6, Table 2). The species differs in a generalized higher count of cephalic scales, in particular the ones listed below (V. berus in parentheses): higher number of crown scales: 7–30, mean 17.4 (versus 4–22, mean 13.0); loreals: 4–15, mean 9.36 (versus 2–12, mean 6.72); and, to a lesser extent, perioculars: 16–23, mean 19.8 (versus 13–23, mean 18.4) (see Table 2). V. walser, in contrast to V. berus, also shows a marked tendency towards fragmentation of the cephalic large shields: the parietal scales are often completely broken down into several smaller scales: 2–14, mean 6.3 (versus 2–10, mean 2.4; see also Fig. 7). Less commonly, also the frontal scale is fragmented into smaller scales. Some individuals exhibit a dorsum of the head covered in small, irregular scales, like in V. aspis. V. walser has between 1.5 and 2 rows of subocular scales on both sides of the head in 85% of the analysed specimens (V. berus has typically one row of suboculars, with the exception of some populations in the southern Alps). The dorsal zigzag is often broken down into separate bars as in Vipera aspis (Linnaeus, 1758) or Vipera berus bosniensis (see Fig. 6). Despite the lack of a strictly diagnostic morphological character, V. walser can be readily distinguished from populations of V. berus from Central and northern Europe by a combination of several characters (e.g. the number of subocular scales, fragmentation of parietals and number of apicals). Identification based solely on observation of external morphology is less obvious if individuals of V. berus from southern Alps are considered. Despite this, discriminant analysis correctly identified individuals to species in 94% of females and 88% of males, based on a set of analysed characters (see Figs 2 and 3). The mean p-distance, based on a combined dataset of about 3000 base pairs of mitochondrial genes, between V. berus and V. walser is 5.36%. Based on our current knowledge of its distribution, Vipera walser is restricted to the Alps north of town of Biella, a subrange of the Pennine Alps, west of the river Ticino, north-western Italy (Fig. 8). The differences in cephalic scale count between Vipera walser and V. berus are shown in Table 2: Crown scales (females: t45,49 = 4.81, p < 0.0001; males: t28,71 = 5.20, p < 0.0001); loreals (females: t94,59 = -7.52, p < 0.0001; males: t62,67 = -4.43, p < 0.0001); and, in females only, perioculars (female: t64,16 = 5.33, p < 0.0001; males: t17,25 = -0.16, p = 0.87) and apicals (females: t32,86 = 2.14, p = 0.04; males: t18,08 = -0.12, p = 0.91); the number of scales between the eyes and the supralabials are higher (females: t66,40 = 5.85, p < 0.0001; males: t37,93 = 7.90, p < 0.0001). |
| Comment | Distribution: see map in Ghielmi et al. 2016: 168 (Fig. 8) Phylogenetics: V. walseri nests within dinniki, kaznakovi, darevskii, ursinii, eriwanensis. Not closely related to V. aspis or V. berus. See tree in Ghielmi et al. 2016: 163 (Fig. 1). However, V. walser is a striking case of mitonuclear discordance (Dufresnes et al. 2024): in the nuclear genome, these populations belong to the alpine diversity of the adder V. berus (as the sister lineage of geographically proximate V. b. marasso), despite carrying mtDNA related to the Caucasian V. kaznakovi complex (Ghielmi et al., 2016). Given this discrepancy, Dufresnes et al. 2024 refrain from synonymizing walser with berus. Previously considered an isolated population of V. berus (Capra, 1954; Sindaco et al., 2006), according to the phylogeny by Ghielmi et al. (2016) V. walser seems surprisingly related to the Caucasian species of the V. ursinii complex. Speybroeck et al. (2020) consider the acceptance of the new species as premature due to the possible existence of mito-nuclear discordance and tentatively regard it as a subspecies of Vipera berus. Freitas et al. (2020) consider V. walser a valid species. |
| Etymology | Named after, and dedicated to, the Walser people with whom it shares an extraordinary beautiful and wild area of the south-western Alps. |
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